This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A241690 #11 Mar 28 2025 13:27:11
%S A241690 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,8,24,80,206,504,1004,1910,3380,
%T A241690 5688,9036,14106,21190,31158,44370,62206,85308,115662,153746,202146,
%U A241690 262156,336960,427488,538690,671604,831926,1021238,1246604,1510056,1820580,2179480
%N A241690 Number of Sidon subsets of {1,...,n} of size 6.
%C A241690 A Sidon set is a set of natural numbers A={a_1,a_2,...}, finite or infinite, such that all pairwise sums a_i+a_j (i <= j) are different.
%e A241690 a(18)=8 since there are 8 subsets of {1,...,18} satisfying the required conditions, for example {1,2,5,11,13,18}.
%t A241690 SidonQ[l__] := If[Length[Join[Plus @@@ Subsets[l, {2}], 2 l]] == Length[Union[Join[Plus @@@ Subsets[l, {2}], 2 l]]], True, False]
%t A241690 Table[Length@Select[Subsets[Range[n], {6}], SidonQ[#] &], {n, 1, 30}]
%Y A241690 Column k=6 of A381476.
%Y A241690 Cf. A054578.
%K A241690 nonn
%O A241690 1,18
%A A241690 _Carl Najafi_, Apr 27 2014